package com.lujian.casual.benchmark;

import org.openjdk.jmh.annotations.*;
import org.openjdk.jmh.infra.Blackhole;
import org.openjdk.jmh.runner.Runner;
import org.openjdk.jmh.runner.RunnerException;
import org.openjdk.jmh.runner.options.Options;
import org.openjdk.jmh.runner.options.OptionsBuilder;

import java.util.concurrent.TimeUnit;


@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@Warmup(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)
@Measurement(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)
@Fork(1)
@State(Scope.Thread)
public class BenchMarkBlackholeHelpers {


        /**
         * Sometimes you need the black hole not in @Benchmark method, but in
         * helper methods, because you want to pass it through to the concrete
         * implementation which is instantiated in helper methods. In this case,
         * you can request the black hole straight in the helper method signature.
         * This applies to both @Setup and @TearDown methods, and also to other
         * JMH infrastructure objects, like Control.
         *
         * Below is the variant of dead code
         * test, but wrapped in the anonymous classes.
         */

        public interface Worker {
            void work();
        }

        private Worker workerBaseline;
        private Worker workerRight;
        private Worker workerWrong;

        @Setup
        public void setup(final Blackhole bh) {
            workerBaseline = new Worker() {
                double x;

                @Override
                public void work() {
                    // do nothing
                }
            };

            workerWrong = new Worker() {
                double x;

                @Override
                public void work() {
                    Math.log(x);
                }
            };

            workerRight = new Worker() {
                double x;

                @Override
                public void work() {
                    bh.consume(Math.log(x));
                }
            };

        }

        @Benchmark
        public void baseline() {
            workerBaseline.work();
        }

        @Benchmark
        public void measureWrong() {
            workerWrong.work();
        }

        @Benchmark
        public void measureRight() {
            workerRight.work();
        }

    /*
     * ============================== HOW TO RUN THIS TEST: ====================================
     *
     * You will see measureWrong() running on-par with baseline().
     * Both measureRight() are measuring twice the baseline, so the logs are intact.
     *
     * You can run this test:
     *
     * a) Via the command line:
     *    $ mvn clean install
     *    $ java -jar target/benchmarks.jar JMHSample_28
     *
     * b) Via the Java API:
     *    (see the JMH homepage for possible caveats when running from IDE:
     *      http://openjdk.java.net/projects/code-tools/jmh/)
     */

        public static void main(String[] args) throws RunnerException {
            Options opt = new OptionsBuilder()
                    .include(BenchMarkBlackholeHelpers.class.getSimpleName())
                    .build();

            new Runner(opt).run();
        }

}
